The invention relates to a fitting for connecting lengths of pipe or tube by compression, having a substantially cylindrical internal contour having at least one ridge which is configured in a radially outward direction and in which a sealing element is provided, the fitting being slidable onto the lengths of pipe or tube.
Fittings of the above kind are known per se. Such fittings comprise a connecting socket in which is formed, to receive a sealing element, an elevation radially shaped outwards into a ridge-like form in cross-section. The elevation serves to receive an end of a pipe or tube. To produce a compression connection, the connecting socket is cold-formed to the pipe or tube by means of a compression tool. In the compression, both the ridge-like elevation with the sealing element situated inside it and also the adjoining regions on both sides of the elevation are deformed almost simultaneously, thus producing a non-releasable, permanently sealed connection.
Following the installation of a piping or tubing system, the system is pressurised in a regulation manner. If a point of connection has accidentally not been compressed, this pressure test normally produces a detectable leak. However, if there are adverse pairings of the tolerances of the fitting, sealing element and pipe or tube, it may happen that when the pipe or tube is inserted in the connecting socket the sealing element is subjected to pressure between the fitting and pipe or tube in such a way that no visible leak occurs. Only in subsequent operation does the uncompressed connection become increasingly leaky due to variations in temperature and pressure, which may result in considerable structural damage, particularly where the system is buried.
DE 102 17 824 C1 discloses a pipe connection, comprising a fitting, which is provided at least with a sealing element, and a line pipe, the end region of which comes to bear against a shoulder of the fitting after it has been slid into or onto the fitting. The line pipe has at least one region extending in the longitudinal direction that differs from the ideal circular shape. After the line pipe is inserted into or slid onto the fitting, there is at least one leakage point between the sealing element and the fitting or between the sealing element and the line pipe, which is closed in a gastight or liquidtight manner after a compressing operation. However, the line pipe of this compression connection is complex to produce. In addition, it causes considerable storage and stockkeeping expenditure. Furthermore, when the line pipe is slid into or onto the fitting, the sealing element may be changed in its functional position, in particular the leakage point may be reduced in its dimensions during the rolling or rotating of the sealing element, whereby the desired effect is greatly jeopardised.
Known from DE 197 22 935 C1 is a compression connection in which there is provided a sealing element having a cross-section lying in the circumferential direction which is given a cross-section which differs, in the form of a projection, from the initial cross-section. This produces a leak in the uncompressed state, which is removed after compression. However, the sealing element of this compression connection is complicated and cost-intensive to manufacture. What is more, the desired effect may be greatly jeopardised if, when the pipe or tube is inserted in the connecting socket, the sealing element is rolled or rotated in such a way that the projection of the sealing element is no longer situated in the functional position intended for it.
DE 101 64 568 C1 discloses a pipe connection, comprising a metallic press fitting, which has at least one section which is intended for receiving a sealing element and is formed in a ridge-like manner in cross-section, and a metallic line pipe with a smoothly formed end region. The sealing element has an identical cross-section which differs from the ideal circular cross-section in all cross-sectional planes. The sealing element is dimensioned in such a way and adopts a position radially in relation to the annular ridge and the line pipe in such a way that there forms a gap, which allows the medium that is to be carried to pass through and is closed in a sealing manner after the compressing operation. The sealing element of this compression connection is likewise very complex and cost-intensive to produce. A deterioration of the desired effect as a result of rolling or rotating of the sealing element also cannot be ruled out.
In DE 100 07 914 C1 is described a fitting for making a compression connection to an inserted end of a pipe or tube, which fitting has an end portion on which is arranged an annular ridge in which a sealing ring is provided. Provided at the ridge is a bulge which sets a spacing between the sealing ring and the wall of the end portion. It is only by the compression of this unsealed point that a sealed connecting arrangement is produced. The bulge is produced by a punch which has for example a spherical portion. This makes the transition from the annular groove to the bulge relatively sharp-edged, which means that, depending on the pairing of tolerances, the sealing element does not flow into the bulge in the desired way and the user must take care to see in what position the compression tool is fitted to the connecting socket.
Known from DE 101 18 955 A1 is a pipe connection comprising a metal compression fitting which has a portion which is of a ridge-like form in cross-section and in which a sealing element is arranged. In the fitted but uncompressed state, the sealing element occupies a position radially with respect to the annular ridge and the pipe which, even allowing for production tolerances on the sealing element, compression fitting and pipe, is of a size such that it produces a gap which allows the medium being carried to pass through, which gap is closed with a seal after compression. Something that is disadvantageous about this compression connection is that only a very small tolerance range is available when the fitting, sealing element and pipes are being produced, which means that production is very complicated and cost-intensive. The possibility of using standard pipes is largely ruled out. What is more, the pipe comes to rest in the connecting socket with a relatively large amount of play, as a result of which the pipe may easily slip out of the connecting socket in the course of further installation prior to the compression. This creates a risk of mis-compression.